Vol. III. MAY, 1887. No. 25. 



G YPSUM ON THE COAST OF LO WER CALIEORNIA. 



There are many localities on the coast of Lower California where 

 gypsum could be obtained. Canoas Point, however, is the prin- 

 cipal place where this sulphate of lime is to be found in great 

 quantities. In the vicinity of this place are numerous marly and 

 argillaceous beds, of a grayish color and very soft, between which 

 are intercalated numerous deposits of gypsum of different thick- 

 ness and in laminated and fibrous masses, with a saline lustre. On 

 a fine, sunny day the bluffs surrounding Cape Canoas glisten and 

 sparkle with light which is reflected from the surfaces of many 

 lamina of gypsum; even the rocks on the beach are covered with 

 a thin deposit of this hydrous calcium sulphate. Farther beyond 

 the bluffs, in the valleys, are also beds of decomposed outcrops of 

 gypsum. 



The formation of the sulphate of lime has, in all probability, 

 originated in this way : 



By the action of air and water, the gaseous masses of sulphu- 

 rated hydrogen from volcanic vents were transformed into sul- 

 phuric acid, and this acid, acting in its turn upon the carbonate of 

 lime of the formation produced hydrous calcium sulphate, or 

 gypsum. 



The country near Canoas Point belongs, in my opinion, to the 

 Eocene period, though north and south of this cape the coast is in 

 many places volcanic, and shows the signs of metamorphism. In 

 botanical aspect the vicinity is very poor, maguey (Agave Shawii) 

 even being absent. Here and there grow only some chollas, 

 echinocacti and milky poisonous bushes of rhus laurina. 



M. Lopateck i. 



A curious sign may be seen in San Diego. On approaching it 

 from one direction it reads : ' Jobbing ;' when facing it directly in 

 front it reads, ' Roofing ;' after passing it by it is found to read, 

 'Tinning.' This is effected by means of coarse perpendicular 

 ribs, which present different surfaces to the eye when seen from 

 opposite directions, but showing both surfaces when viewed di- 

 rectly in front 



